1. Field of the Invention
This invention relates to an image forming apparatus, and more specifically, to an electrostatic copying machine in which image information on a document is focused on an image bearing member to form an electrostatic latent image thereon, and a copy image is obtained by developing the latent image.
2. Description of the Related Art
In general, a copying machine includes an image reading section, an image forming section, and a paper feeding section.
The image reading section includes a document table used to carry the document to be read thereon, an illumination unit for illuminating the document, and an optical system for transmitting the reflected light from the document. In the image reading section, an image on a document is illuminated, and a reflected light from the document is guided to an image bearing member.
The image forming section includes a photoconductor, i.e., the image bearing member, on which an electrostatic latent image is formed by means of the light from the image reading section, and which serves to reproduce the image of the document. The image forming section further includes a charging unit, developing device, transfer unit, fixing unit, cleaning unit, etc, as well as the photoconductor. The photoconductor, which is arranged for rotation, produces the electrostatic latent image corresponding to the light transmitted by means of the reading section. The charging unit is used to charge the photoconductor with electricity. The developing device develops the latent image on the photoconductor into a visible image. The transfer unit transfers the developed image to the copying material, and the fixing unit fixes the transferred image on the copying material. the cleaning unit is used to restore the photoconductor to its initial state.
The paper feeding section includes a plurality of paper cassettes for supplying the paper sheets, a paper feeder for feeding the paper sheets in the cassettes into the image forming section, and a discharge section for discharging each paper sheet having the copy image thereon. The paper feeding section is used to supply a copying material, e.g., sheet like plain paper, to the image forming section, transfer the image obtained in the image forming section to the plain paper, and discharge the resulting copy.
In the copying machine described above, a predetermined electric charge is applied to the photoconductor by means of the charging unit. Image information on the document, that is, the reflected light from the document, is transmitted through optical members, such as a plurality of return mirrors, a focusing lens, etc., to be focused on the surface of the photoconductor. This reflected light produces a charge distribution pattern or electrostatic latent image, which corresponds to the document image, on the photoconductor. The latent image is supplied with a developing agent, such as a toner, to be developed by means of the developing device, that is, it is copied as the image on the document. This toner image is transferred to the piece of the paper sheet fed from the paper feeder, the toner is fixed by means of the fixing unit, and the paper is discharged from the copying machine.
The copying machine of this type uses a conventional method for allowing only a specific user or users to make copies. One example of this method is disclosed in Published Examined Japanese Utility Model Application No. 61-34529. According to this method, copying is allowed by attaching an external device, such as a key counter, to the machine. This method is used in the case where many divisions have one copying machine for common use, so that the number of copies may have to be checked for each division, or that each division may be expected to bear the cost of copying depending on the number of copies made thereby.
If the key counter is used, copying operation is inhibited by removing it. In this case, however, the copying operation can be only inhibited, and copying conditions used last are maintained as they are. This implies that another user may be forced to use undesired copying conditions. If a copy starting signal is inputted without ascertaining that copying conditions to be newly used are different from the last-used ones, moreover, expendables such as the copying paper and toner will be wasted, thus entailing an increase in the cost of copying.